1. Field of the Invention
The present invention relates to a control method for a power transmission device of an internal combustion engine.
2. Description of Background Art
In a power transmission device for transmitting rotational power from a crankshaft of an internal combustion engine to an output side by way of a clutch mechanism and a speed change mechanism, the internal combustion engine is started by a starter in a state wherein the clutch mechanism is in a disengaged state. In addition, the internal combustion engine assumes an idling state at a steady-state idling rotational speed. At this time, cranking is also finished.
In such an idling state, the speed change mechanism is changed over from a neutral state to a first speed gear, and the clutch mechanism is brought into an engaged state thus transmitting the power to the output side of the speed change mechanism.
In the idling state of the internal combustion engine, the clutch mechanism is in a disengaged state. However, when a clutch input side of the clutch mechanism is rotated due to the rotation of the crankshaft, a clutch output side of the clutch mechanism is rotated together with the clutch input side by friction. In addition, a speed change drive side of the speed change mechanism which is continuously connected with the clutch output side is rotated. Thus, when the speed change mechanism is changed to the first speed gear from the neutral state, a speed change driven side which is not rotated is momentarily engaged with the rotating clutch output side and the speed change drive side which are rotated due to a rotational inertia thus generating impacts and noises.
Various kinds of techniques have been proposed for preventing the generation of impacts and noises. See, for example, Japanese Patent No. 3509243.
A power transmission device disclosed in Japanese Patent No. 3509243 includes a brake mechanism for performing braking by bringing a brake shoe into contact with a clutch outer (clutch output side) of a start clutch only when a speed change mechanism is changed over from a neutral state to a first speed gear.
More specifically, in changing over the speed from the neutral state to the first speed gear, by applying braking to the clutch outer of the start clutch thus preventing the co-rotation of the clutch outer, the speed change drive side and the speed change driven side, which have no relative rotation or exhibit a small difference in rotational speed therebetween, are engaged with each other. Thus, there is no possibility that impacts and noises are generated.
However, it is necessary to additionally provide the brake mechanism which performs braking by bringing the brake shoe into contact with the clutch outer of the start clutch only when the speed change mechanism is changed over from a neutral state to a first speed gear. Thus, the number of parts is increased and the surrounding of the clutch mechanism becomes complicated thus increasing the cost.